MX2008002992A - Method and apparatus for removing a fugitive pattern from a mold. - Google Patents

Abstract

A fugitive pattern, such as wax or other meltable pattern material, residing inside of a refractory mold, which can be unsupported or supported in a particulates bed, is removed by discharging steam or other condensable vapor that may include a surfactant inside the mold to contact and melt the pattern while an exterior of the mold is subjected to a non-condensing gas atmosphere such as air outside of the mold. Regardless of whether the condensable vapor includes surfactant or not, the mold can be tilted relative to gravity and rotated while it is tilted to improve the pattern removal. Condensable vapor is condensed inside the mold where the vapor has contacted the pattern while the exterior of the mold remains free of condenate. The condensed vapor and melted pattern material are drained out of the mold with the surfactant, if present, improving drainage.

Description

METHOD AND APPARATUS TO REMOVE A FUGITIVE MODEL OF A MOLD Related Request This request is a continuation in part of the copending application no. No. 10 / 899,381 filed July 26, 2004. Field of the Invention The invention relates to a method and apparatus for removing a fugitive model from a metal casting mold. BACKGROUND OF THE INVENTION The well-known investment casting process of "lost wax" typically uses a refractory mold that is constructed by the accumulation of successive layers of ceramic particles unit with an inorganic adhesive on a material for a fugitive model (disposable ) such as typically a wax, plastic or the like. The finished refractory mold is usually formed as a shell mold around a fugitive model. The refractory shell mold that resides on the fugitive model is typically subjected to a removal operation of the model, whereby the model melts and leaves the shell mold. This operation leaves a "green" empty refractory shell mold (without baking). Fugitive model materials typically have a thermal expansion rate many times greater than that of the refractory shell mold. If the fugitive model and the refractory mold is heated uniformly, the material of the fugitive model will expand thermally more than the refractory mold. This will put the refractory shell mold under a strain and finally fracture it. The avoidance of mold fracture is the reason why the removal of material from the fugitive model has typically been done by methods such as high-pressure steam autoclaving by removal of models by instantaneous baking. The removal of the material from the fugitive model by means of a high-pressure water steam autoclave or by an instantaneous baking is performed to expose the outer part of the refractory shell mold at high temperatures. This high temperature causes heat to be conducted through the refractory shell mold more quickly to melt the surface of the model before the interior of the model expands thermally. This surface layer of the molten model material extends completely to where the model is exposed in the open part of the mold and causes the pattern material to expand inside the mold by forcing some of the liquid surface pattern material out of the hole of the mold. Those methods can still allow the refractory shell mold to fracture if the heat is not applied continuously along the surface of the fugitive model inside the mold. When connecting the refractory shell mold between adjacent models, this is one of the main causes of non-uniform heating of the model. This is the thicker regions of the refractory shell mold will prevent the application of Heat to the model material will locally delay the casting of the model surface and interrupt continuity. This prevents the passage of the surface liquid pattern material from a thinner mold region farther from the mold hole than the thicker mold region. This prevention of the passage of material from the surface liquid model causes an accumulation of the model pressure in the remote thinner mold region due to the thermal expansion of the model material and can lead to the mold fracturing. These problems require the use of a sufficiently strong mold (eg thick enough) to withstand the expansion pressure of the model material and often require the use of additional holes or vents through the mold to relieve the pressure of the expansive models not connected Stronger or thicker molds as well as the ventilation method are undesirable since they raise processing costs. A plurality of refractory shell molds (air standards) is typically loaded in a charge or hot continuous furnace by means of gas or oil combustion and heated to a temperature of 871.11 ° C to 1, 093.33 ° C. Alternatively, the mold can be heated by means of a method according to U.S. Patent 6,889,745 of the same assignee herein, which describes the heating of a mold with or without support sand surrounding the mold. The hot refractory molds are removed from the furnace and the molten metal or alloy sneaks into them.

The tendency in inverted cast iron is to make the refractory shell mold as thin as possible to reduce the cost of the mold as described above. The use of refractory shell molds has required the use of support means to prevent mold failures as described by Chandley et. in the US patent 5069271. The patent 271 describes the use of adhered ceramic shell molds made the thinnest possible for example with a thickness less than 0.30 centimeters. The unbonded support particulate media is compacted around the hot refractory shell mold after it is removed from the preheat oven. The non-adhered support means resists the forces applied to the shell mold during casting to prevent mold failure. However, thin shell molds have a greater tendency to fracture during the operation of the model, such as the operation of removal of model in steam autoclave at high pressure or instant baking mentioned above, in which the model It melts from the shell mold. The copending application no. of series 10 / 899,381 filed on July 26, 2004 describes a method for removing a fugitive model from a refractory mold adhered to by discharging condensable vapor such as steam, into the mold to make contact with and melt the model while the exterior of the mold is subjected to an atmosphere of non-condensing gas, such as air environmental outside the mold. The condensed steam and molten model material are drained from the mold in a manner that reduces fracture in the mold. Brief Description of the Invention One aspect of the present invention provides a method and apparatus for removing a fugitive model, such as wax or other meltable model material, resident in a refractory mold by introducing a condensable vapor, such as steam, which in a particular embodiment it includes a surfactant within the mold to make contact and melt the model, while the exterior of the mold is subjected to a non-condensing gas atmosphere, such as ambient air, outside the mold. The condensed steam and molten model material drain out of the mold. The surfactant reduces the surface tension of the condensed vapor in contact with the fugitive model within the mold and increases the ease with which the material of the molten model flows onto the interior surface of the newly exposed mold to improve drainage of the molten model material out of the mold, leaving less residual model material inside the interior surface of the mold. A pressure difference between the condensable vapor inside the mold and the non-condensing gas atmosphere outside the mold is small enough to prevent the condensable gas from leaking out from the outside of the mold and the non-condensable gas to enter the cavity of the mold. mold. The condensable vapor inside the mold and the gas atmosphere outside the mold preferably have substantially the same pressure for this purpose. In this way when steam is used as the preferred condensable vapor, the steam condenses within the mold where the steam has made contact with the model while the exterior of the mold remains dry. The condensable vapor, the vapor condenses inside the mold where the steam has made contact with the model while the outside of the mold remains dry. The condensable vapor that includes the surfactant can be introduced into the mold at atmospheric, subatmospheric or superatmospheric pressure depending on the melting point of the model material. An illustrative embodiment of the invention, vapor or other condensable vapor is supplied to a discharge tube that can be placed inside the nozzle for the mold and / or the model for discharging water vapor or condensable vapor at atmospheric, subatmospheric or superatmospheric pressure. . The surfactant can be introduced into the condensable vapor in the discharge tube or out of the discharge tube after the condensable vapor is discharged. Another aspect of the present invention provides a method and apparatus for removing the fugitive model, such as wax or other meltable pattern material, resident in a refractory mold by subjecting the mold to a combination of rotation and tilting (turning) during the removal process of the model in a manner that improves the drainage of molten model material of the mold. The mold can be tilted at any desired angle using a mold with a Tilt drive motor and the mold can rotate around an axis using a mold rotation drive motor. The angle of the mold inclination and the rotation speed of the mold can be adjusted as required to drain the molten wax from the mold cavities. The mold can be rotated while the mold is tilted at an angle of inclination in relation to gravity. Alternatively, the mold can be inclined increasingly up to the selected inclination angles while the mold is rotated at each inclination angle or continuously. In addition the mold can be continuously tilted. In addition, the mold can be continuously tilted by rotating continuously or intermittently. Water vapor or other condensable vapor can be introduced to heat and melt the furtive pattern within the mold while the mold is subjected to rotation and tilting, although this aspect of the invention can be practiced using any model challenge technique where the model melts or dissolves. The above embodiments of the present invention can be practiced to remove a fugitive model, such as wax and other material for the meltable model, from a non-sustained casting mold. The present invention can also be practiced to remove a fugitive model from a casting mold held in a particulate medium in a container. For example, steam or other condensable vapor is introduced into the mold to make contact and melt the model while the outside of the mold makes contact with the particulate medium and is subjected to an atmosphere of non-condensing gas (for example steam-free), condensed vapor inside the mold where it makes contact with the model while the exterior of the mold and the surrounding particulate medium is subjected to a non-condensing gas atmosphere and draining the molten model material and condensed vapor out of the mold. The invention is advantageous for removing one or more fugitive models resident in a refractory mold for the melting of metals, which may have any thickness of mold wall and which may or may not be supported by the outer particulate medium surrounding it. The invention is also advantageous for removing one or more fugitive molds while avoiding to saturate the mold wall with steam or other condensate, which can have an adverse effect on the binder used to make the mold. The invention can be made to reduce the fracture of the mold during the removal of the model and to remove the model material from the molds where the vapor or can easily access the exterior of the mold wall for example when the mold is held with the mold. medium of support in particles. These and other advantages of the invention will be apparent from the following detailed description taken in conjunction with the following drawings. Brief Description of the Figures Figure 1 is a schematic view of a refractory mold for casting having fugitive models to be removed according to an illustrative embodiment of the invention by discharging steam at atmospheric pressure including a surfactant from a shown discharge tube placed in a hollow nozzle of a resident model assembly within the mold . Figure 1A is a schematic view of a refractory casting mold having fugitive patterns that are to be removed according to another illustrative embodiment of the invention when discharging the vapor at atmospheric pressure and a surfactant of separate discharge tubes shown placed in a hollow nozzle of a model assembly resident within the mold. Figure 2 is a schematic view of the refractory casting mold of Figure 1 with the hollow nozzle of the fugitive model assembly already removed by means of melting and with the gates and individual models melted and removed. Figure 3 is similar to Figure 2 after the models have been completely removed from the shell mold. Figure 4 is an enlarged view of an individual model of Figure 2 illustrating removal of the model. Figure 5 is similar to Figure 1 but shows a model assembly having a solid nozzle with a steam discharge tube that moves in the solid nozzle to form a hollow nozzle in situ. Figure 6 is a schematic view of a casting mold refractory having fugitive patterns to be removed according to another illustrative embodiment of the invention in which the mold is externally supported by means of a particulate support means surrounding it. Figure 7 is similar to Figure 1 shows a refractory casting mold having fugitive patterns to be removed according to another illustrative embodiment of the invention when discharging steam at a superatmospheric or subatmospheric pressure from a steam discharge pipe shown in FIG. a hollow nozzle of a model assembly resident within the mold. Figure 8 is a perspective view of an apparatus for subjecting a mold to rotation and tilting during the model removal process according to another illustrative embodiment of the invention. Figure 9 is an elevational view, partly in section of the apparatus of Figure 8. Figure 10 is similar to Figure 9 showing the mold inclined in relation to gravity. Figure 11 is an enlarged perspective view of the upper part of the mold support by means of which a lower end of the mold is supported rotatably. Figure 12 is an enlarged perspective view of the bottom of the mold support by means of which the end of the mold is supported rotationally.

Detailed Description of the Invention The present invention improves the method and apparatus for removing one or more resident figurative models within a refractory mold as described in copending patent application no. series 10 / 899,381 filed July 26, 2004, the description of which is incorporated herein by reference. In particular, one embodiment of the present invention includes a method and apparatus for removing one or more resident fugitive models within a refractory mold by introducing a condensable vapor that includes a surfactant within the mold. The condensed steam and molten material of the model are drained from the mold. The surfactant reduces the surface tension of the condensed vapor in contact with the fugitive model within the mold and increases the ease with which the molten material of the model flows through the interior surface of the newly exposed mold to improve drainage of the molding material towards out of the mold, leaving less residual model material on the surface of the mold. The method is especially useful for removing one or more fugitive molds from within the cast-iron ceramic mold for casting by gas-permeable "lost wax" inversion, although the invention is limited to the implementation to remove one or more models fugitives from other types of refractory cast metal molds having one or more fugitive models inside, which may have any wall thickness of mold and which may or may not be supported by an outer particle means which surrounds When the steam is used as a preferred condensable vapor, the invention can be made to remove one or more fugitive models which may consist of conventional wax models and other model materials melted at a temperature below the boiling point of the water (eg example approximately 104.44 ° C) under particular ambient atmospheric pressure conditions present during the model removal operation. The invention can also be practiced to remove one or more fugitive models which may consist of conventional wax models or other model materials and which melt at a temperature above the boiling point of the water when using superatmospheric steam for this purpose during the operation of removing models according to another embodiment of the invention described below. In addition, the invention can be practiced using subatmospheric pressure steam to remove one or more fugitive models that may require lower temperatures to melt them. Alternatively, when practicing the invention, the vapor can be replaced by means of a condensable vapor of another suitable material, such as for the purposes of illustration and not limitation, mineral spirits with a boiling point of about 148.89 ° C where the Steam can condense and heat the fugitive model when it makes contact with the model for the purpose of melting and removing the model.

For illustrative and non-limiting purposes, one embodiment of the present invention will be described below in connection with FIGS. 1-4 with respect to removing a plurality of patterns should be attached by means of a respective gate 35 to a central hollow nozzle 30 of FIG. a model assembly 40 from the inside of a shell mold for "lost wax" investment casting 20. In figure 1, the hollow nozzle 30 comprises a preformed wax nozzle having an axially elongated inner chamber 30a and It has models 10 joined by means of welding with wax or a fixing technique to its outer surface 30s. For the purpose of illustration and not limitation, the wax nozzle 30 can be made to have the inner chamber 30a by means of molding, extrusion, by initially forming the nozzle in a cylindrical mandrel or otherwise substantially removing it on heating. mandrel and thus to the adjacent wax to allow the mandrel to be physically extracted, when drilling a solid wax nozzle or by any other suitable technique. Although two models 10 are shown in Figure 1, those skilled in the art will appreciate that additional models 10 are typically attached around the nozzle 30 in the same place as the models 10 but are not seen in Figure 1 as a result of their view in section. In addition, the additional models 10 can be attached by means of gates around the nozzle 30 in other axial locations along their length (for example the previous models 10 shown in Figure 1) as is known and is shown for example in U.S. Patent 5 069 271, the description of which is incorporated by reference. Referring to Fig. 1, a shell mold 20 for "lost wax" inverted casting is shown inverted in a plurality of wax patterns 10 attached by means of gates 35 around a central wax nozzle 30 by means of the conventional process of "loss wax" for producing shell molds as described, for example in U.S. Patent 5 069 271, wherein the molding assembly 40 including the models 10 attached by the gates 35 to the hollow nozzle 30 is repeatedly immersed in a refractory slurry having a binder, lined with refractory stucco particles and dried to form the shell mold on the model assembly. The patent discloses a gas permeable thin walled shell mold having a mold wall thickness of about 0.32 centimeters or less. That thin-walled mold 20 as described in the patent can be held in a casting container 60 by particulate support means 50 (eg ceramic particles) as shown in Figure 6 during the pattern removal operation. The invention is not limited to the practice with that thin-walled shell mold supported by a particulate medium, and on the contrary it can be made with a refractory mold with any mold wall thickness, whether it is externally supported by a medium of particle support is not sustained as shown in figure 1.

The shell mold 20 is shown inverted (this is oriented upside down) to allow molten model material and condensed steam to drain by gravity from the lower end of the nozzle 30. The mold 20 can be placed in other orientations that facilitate the drainage of the molten model material and the condensed vapor out of the mold. Further, the mold 20 can be moved during the removal operation of the model in a manner that facilitates the drainage of the molten model material and the condensed vapor out of the mold. Referring to FIG. 1, according to an illustrative embodiment of the invention, a pipe or a discharge tube 100 connected to a surfactant supply conduit 101 is shown positioned in the elongate chamber 30a of the hollow nozzle 30 of the model assembly 40 for introducing a stream (represented by the steam arrow "A") that includes a surfactant (represented by the arrow "SF") with a substantially atmospheric pressure inside the nozzle hollow 30 of the model assembly 40 for contacting and melting the wax model assembly while the outer surface 20s of the mold 20 is subjected substantially to the ambient atmospheric air pressure (represented by the "ambient pressure"). The ambient air that forms a non-condensing ace atmosphere around the mold 20 in Figure 1 can be room temperature or can be cooled relative to room temperature. A typical wax material from which the model 40 assembly is made is made melt and becomes fairly fluid at approximately 82.22 ° C for illustrative and non-limiting purposes. Steam at a substantially atmospheric pressure is generated in a steam source 110, which may consist of a commercially available conventional steam generator such as model LB240 from The Electro Steam Generator Corp. Steam flows from the generator or the source of steam. steam 110 through a feed tube 120 to the steam discharge pipe 100. The steam flow from the source or the generator 110 can be supported by adjusting by adjusting the pressure in the steam generator so that adequate steam will flow to the steam generator. through the tube to the mold to replace the amount of steam that has condensed. The SF surfactant is introduced into the vapor discharge tube 100 through the surfactant feed line 101 connected to a surfactant feed pump 111. The pump 11 pumps the surfactant from a feed tank T. The surfactant in the Tank T typically has a diluted form; this is the surfactant is diluted to a selected concentration in a liquid carrier vehicle. The flow of the SF surfactant in the conduit 101 is regulated by using the surfactant measuring pump 111 or a valve arrangement to control the flow rate of the surfactant from an appropriate surfactant feed pump. For example, an alternative apparatus and method for introducing SF surfactant into tube 100 may involve supplying liquid surfactant at a constant pressure to a valve.

Adjustable and regulate the flow of surfactant in tube 100 through the use of an adjustable valve. Although the SF surfactant is described as being introduced into the vapor within the discharge tube 100, the invention is not limited thereto. For example, the surfactant can be introduced outside the vapor discharge tube 100 using a second discharge tube of the second surfactant 100 'as shown in Figure 1A. The surfactant discharge tube 100 'extends into the mold in a manner that the SF surfactant is introduced downstream of the end of the steam discharge tube 100 and into the vapor stream after it is discharged from the end of the tube. of discharge 100 into the mold as shown in Figure 1A. For the purpose of illustration and not limitation, an exemplary surfactant for use in the practice of this aspect of the invention comprises Tomadol which is a liquid surfactant of non-ionic alcoholic staxilate grade 1-4, which is marketed by Tomah Products, Inc., Milton, Wisconsin and diluted to 0.5% by weight of solution in water (carrier vehicle) and added at a rate of 60 ml / min to the vapor stream in the discharge tube 100 via conduit 101. The surfactant it is added to the discharge pipe 100 in such a way that it will be present in the steam inside the mold as the mold wall melts during the removal process of the model. The invention is not limited to the practice with the exemplary surfactant described above since other non-ionic surfactants than others concentrations in the vapor or condensable vapor. In general, the surfactant and its concentration in the condensable vapor are selected to reduce the surface tension of the condensed vapor that is in contact with the fugitive model within the mold to increase the ease with which the molten model material flows on the inner surface of the newly exposed mold, improving the drainage of molten model material towards. outside the mold to leave less residual pattern material on the surface of the mold. In addition, although in the previous paragraph water is described as the carrier vehicle for the surfactant when the condensable vapor consists of water vapor, the invention is not limited thereto. The surfactant can be transported in a dilute form using any liquid vehicle that is compatible with a particular non-aqueous condensable vapor that is being used. For exampleWhen the condensable vapor consists of mineral alcohols, the carrier vehicle may contain mineral spirits. The water vapor at the substantially atmospheric pressure and containing the SF surfactant is discharged into the chamber 30a at a sufficiently high flow rate to displace the air from the chamber 30a and progressively contact and melt the model material of the wax nozzle 30 and then the gates 35 and the models 10.1a flow rate of the steam discharged into the chamber 30a can be varied during the removal of the nozzle and the models depending on the rate of condensation of the water vapor inside the mold. This rate will depend on the surface area of the wax exposed to steam in the point during the removal of the wax, and the size of the mold. When multiple rows of models and gates are attached to the nozzle along its length, the steam progressively fuses uniformly in the model material of each model uniformly from the gate and consequently advances towards the model. During the invention, the age nozzle 30 may not be present or may be removed by other means prior to removal of the models 10 upon contact with the vapor. This is only the models 10 are present in the shell mold 20 having an empty central nozzle-shaped passage, then the steam discharge tube 00 is placed to discharge the steam into the mold 20 to make contact with and melt only the models 10 and the associated gates 45. Figure 2 and 4 illustrates the process of removing models after the central hollow nozzle 30 has been fused and removed and while the gate 35 and the model 10 are fused and removed. The vapor containing the surfactant is shown removed to gate 35 and the associated model 10 as the steam condenses when the steam has melted the wax model. In particular, as the vapor condenses on the surface of the gate and the model, a relatively lower pressure is generated in the V region near where the material of the gate and / or model melt to cause the steam cool downstream flow down towards the region of the gate and the model that has melted The molten liquid wax material partially stages the surface of the inner mold wall as illustrated in the surface region S and acts as a barrier to prevent vapor condensate from soaking the entire thickness of the mold wall W. In addition, the presence of atmospheric air pressure on the outer surface 20s of the mold 20 does not provide driving force to cause the steam condensate to pass through the mold wall, preventing saturation of the mold wall with the condensate of the mold. vapor and the adverse effects on the binder present in the mold wall. During the model removal operation, as a result the outer surface 20s of the mold exposed to ambient air (such as a non-condensing gas atmosphere) remains dry (without liquid water). A pressure differential between the condensable vapor inside the mold 20 and the non-condensing gas atmosphere outside the mold 20 is small enough to prevent the condensable gas from flowing out of the mold through the wall of the gas permeable mold W and that the non-condensing gas enters through the wall W into the mold cavity occupied by the fugitive model assembly being removed. The condensable vapor inside the mold and the non-condensing gas atmosphere outside the mold preferably for this purpose are substantially at the same pressure. In Figure 4, the inclusion of the surfactant with the condensable vapor (for example the vapor of atmospheric pressure) results in the wetting of the vapor condensate to the mold refractory soaked with wax and the formation of a surface layer of vapor condensed along the surface of the refractory wall soaked with wax. The molten wax model material is drained from the model area being melted, consequently flowing in a condensed vapor layer which due to its low viscosity allows the molten wax to flow more easily along the mold wall and towards outside the mold cavity. This results in a faster removal of the model material from the mold cavity and less residual pattern material remaining in the mold cavity. As further illustrated in Figure 4, the vapor condensate and the molten wax model material are drained out of the mold 20 by gravity through the nozzle gap or passage P created when the wax nozzle Hollow 30 has been removed. The molten wax model material may be collected in or on a collection tray or container (not shown) positioned below the mold 20 in Figure 1. A mold axis 20, such as the longitudinal axis L of the mold 20 of Figure 2, which contains the fugitive model can be tilted with respect to the direction of gravity during the casting of the fugitive model or after the fugitive model has been melted. Water vapor at substantially atmospheric pressure is believed to only produce a small affected zone Z in the wax model such that the remaining portion of the solid wax model 10 remains relatively unaffected by steam, although the Applicants do not wish to stick to any theory in this case. This small area of hot but not molten model material is free to thermally expand to the molten surface, resulting in reduced or no stress on the refractory mold surrounding it. The thermal expansion of the wax inside the mold is the reason why the mold fractures during the wax removal by means of a standard autoclave. The discharge of the vapor and surfactant SF from the steam discharge tube 100 into the mold is continued even though the complete model assembly 40 (including the nozzle 30 and the 10 models) melts and is removed from the mold 20, leaving a empty shell mold 20 which includes a plurality of mold cavities MC connected to the nozzle passage P as shown in Figure 3. The mold is then ready to be baked at a suitable temperature to prepare the mold to receive the molten metal or the alloy to be cast in the mold as is well known and does not form part of the invention. Although the chamber 30a of the hollow nozzle 30 is described above as being made in connection with FIGS. 1-4, the invention is not limited thereto. As shown in Figure 5, a chamber 30a 'can be formed in situ in a solid wax precursor nozzle 30' of the model assembly, Figure 5, by axially moving the discharge tube 100 relatively in such a way that the vapor discharged at the atmospheric pressure of the tube 100 and including the surfactant of the tube 101 strikes against the opposite end 30e 'of the solid nozzle 30 'and progressively melt away from chamber 30a' in situ at the solid precursor nozzle 30 '. After the chamber 30a 'is formed, the withdrawal of the now hollow nozzle 30' and the models 10 can be performed as described above in connection with Figures 1-4. In Figure 5, like reference numbers are used for similar characteristics of Figures 1-4. In another embodiment of the invention illustrated in Figure 6, a fugitive model assembly 40 is removed from a thin wall and another refractory mold 20 which is externally supported or surrounded by a particulate support means 50 in a casting container 50 as is described in U.S. Patent 5 069 271. The particulate media 50 may comprise ceramic particles or clay as described in the patent. The removal of models is effected by discharging steam at substantially atmospheric pressure from the steam discharge tube 100 and contacting the surfactant of the tube 101 within the hollow nozzle 30 of the model assembly 40 to contact and melt the hollow nozzle. 30 and then the models 10 as described for claims 1-4. The outer surface 20s of the mold 20 makes contact with the particulate medium 50 and is subjected to substantially atmospheric atmospheric pressure by means of venting to the atmosphere 61 in the casting container 60 during removal of the model. The outer surface of the mold 20s and the particulate medium 50 remains dry (free of liquid water) as a result of the molten vera partially extending into the wall of the mold W as it is described above with respect to Figures 1-4 and to prevent the condensed vapor from soaking the entire thickness of the mold wall. For illustrative and non-limiting purposes, another embodiment of the method of the present invention shown in Figure 7 will be described below in which the superatmospheric or subatmospheric pressure vapor is discharged into the mold to remove the model assembly 240 having a plurality of wax patterns 210 joined by means of the respective gate 235 to the central hollow nozzle 230 from the inside of the shell mold for inverted casting by "loss wax" 220. The use of superatmospheric pressure steam while the exterior of the mold is subjected to the non-condensing gas under substantially the same superatmospheric pressure allows an increase in the heat capacity per unit volume of the steam and thus allows the melting of model materials with higher melting point. The use of subatmospheric pressure steam while the exterior of the mold is subjected to non-condensing gas at substantially the same subatmospheric pressure allows the melting and removal of model materials which for example require lower temperatures. The following method modality will be described using superatmospheric pressure steam including SF surfactant, although the modality of the method can also alternatively use steam at superatmospheric pressure. The mold 220 is disposed within a pressure vessel 250 over a collection basin 252 to collect and contain the era. melted and the condensed vapor that leaves the mold during the operation of withdrawal of models. The pressure vessel 250 may consist of a casting container of the type including particulate support means around the mold 220 as illustrated in Figure 6. Alternatively, the pressure vessel 250 may be free of the particulate support means; this is empty with only the shell mold inside. The pressure vessel 250 can be formed with a suitable pressure resistant material such as steel and configured as a typical conventional pressure vessel. A casting chamber 60 and the mold contained therein as shown in Figure 6 can also be placed inside a separate pressure vessel 250 for removal of superatmospheric pressure wax. A seal 254 is provided between the mold 20 and the pressure vessel wall 250a to substantially prevent mixing of the gas from the inner region of the seal 254 to the exterior of the seal 254. The seal 254 may comprise a steel member or other tubular member. 254t having a rubber seal or other type of seal 254a for sealing the mold 220. Steam at superatmospheric pressure and including the surfactant from the tube 101 is discharged into the mold 220 from the discharge tube 300. The tube 300 it is connected to a source S of the steam at superatmospheric pressure, such as the previously described steam generator and extends through a hole in a wall 250a and also to a conduit pair at the entrance of surfactant 101 as shown in Figure 5. Simultaneously with the discharge of the superatmospheric pressure vapor inside the mold 220, the air pressure at substantially the same pressure as the vapor pressure inside the mold is provided in the pressure vessel 250 by means of from an input 255. Input 255 for superatmospheric air pressure is connected to a source of compressed air, such as an air compressor; for example the Kaeser compressor model SP 25. This method modality includes discharging steam including the surfactant from the tube 101 into the mold 220 to contact and melt the pattern material while the exterior of the mold 220 is subjected to a gas atmosphere steam-free outside the mold wherein the vapor inside the mold and the vapor-free atmosphere outside the mold are substantially at the same pressure. The pressure of the corresponding vapor and air (or other gas) can be adjusted to any pressure (and therefore temperature) appropriate for rapid melting of the model material. The superatmospheric pressure within the pressure vessel may be provided by means of a gas other than air such as, for example, nitrogen, inert gas, or other gas at the desired superatmospheric pressure substantially equal to that of the vapor within the mold. An air evacuation valve 256 is provided in the wall of the pressure vessel 250 to reside in the region within the seal 254 to eject the air that was initially inside the mold 220 of the region within seal 254. The withdrawal operation of the model of the embodiment of Figure 7 proceeds as described above with respect to the atmospheric pressure of the vapor discharged with the surfactant into the mold 20 where the superatmospheric vapor makes contact with the solid wax material of the model assembly and it is condensed. More heat is supplied to the surface of the wax in this embodiment of the invention since the superatmospheric steam is at a higher temperature when it is compressed. A slightly reduced pressure is formed on the surface of the wax when the steam condenses, which causes more steam to make contact with the surface of the wax to facilitate the removal operation of models. The molten wax from the surface of the wax and the condensed vapor flows out of the mold cavity and into the wax collecting tray and the condensate 252. The wax removal action occurs only internally in the mold 220 in an ordered manner from the nozzle 230 to the gates 235 and then in the wax models 210. The seal between the mold and the pressure vessel 254 results in no steam being applied to the outside of the mold 220 in the pressure vessel 250. A vapor-free atmosphere is provided in the pressure vessel 250. Referring to Figures 8 to 12, another aspect of the invention is illustrated in which the unsupported shell mold 500 (Figure 10) is subjected to a combination of rotation and tilting in relation to gravity during the removal process of the model using steam or other condensable vapor in the manner described above with or without including a surfactant in water vapor or other condensable vapor. This mode is not limited to removing the model using water vapor or other condensable vapor and provides that other techniques of withdrawal of models can be used while the mold is subjected to a combination of rotation and inclination. For example, a stream of hot air or gas can be introduced into the mold in a manner that warms and fuses the model while the mold is subjected to a combination of rotation and tilt. The mold can also be located in a furnace to instantly warm the model while that the mold is subjected to combined rotation and inclination. In addition, a chemical dissolving medium can be introduced into the mold to contact and dissolve the model while the mold is subjected to combined rotation and inclination. Likewise, this additional aspect of the invention can be practiced to remove one or more fugitive models from a mold that is externally supported or held by a surrounding particle medium in a casting container as described above in connection with Figure 6 and also in the North American patent no. 5069271. In Figure 10, there is shown an unsupported shell mold 500 having a plurality of fugitive (e.g., wax) models 510 disposed about and along a fugitive nozzle (e.g., wax) 520. Each model is sample connected to the nozzle by means of a gate 535. The rotary action about the longitudinal axis L of the mold while the mold is inclined in relation to the gravity shown in figure 10 according to this aspect of the invention allows the molten model material to be drain evenly from all MC pattern cavities that are arranged around the central nozzle passage P when the model and nozzle are removed. Figure 8 shows an apparatus illustrative of the embodiment of this aspect of the invention before the mold 500 is placed in the apparatus. Figure 9 shows the apparatus before the mold 500 is placed in the apparatus and before the mold is tilted with respect to gravity. Figure 10 shows the apparatus after the mold is placed in the position and inclined with respect to gravity in such a way that its longitudinal axis L is oriented at an angle of inclination. In practicing this aspect of the invention, the mold 500 having the fugitive pattern and the nozzle is placed there between an upper mold jaw and the rotation mechanism 510 and a lower mold support mechanism 512. The shell mold 500 includes an upper annular collar 500 c receiving an end 510e of the upper mold clamp mechanism 510 as best shown in Figure 10. The end 510e closes the nozzle passage of the mold P. The mold includes a lower annular collar 500d received in a rotating nest 512n disposed on a support plate 512p of the mold support base 512b as shown better in Figures 10 and 11. The mold support base 512b is fixed to the side arms A of the frame F of the apparatus. A crossbar plate P3 is provided between the arms A. The mold collars 500c, 500d can be formed integrally with the mold 500 or can be formed separately and attached to the mold. One end of the pipe or water vapor supply tube 500 extends upwardly through a hole in the mold support base 512b and the support plate 512p to communicate with the open bottom end of the mold 500 as shown in FIG. shown in Figure 10 for introducing water vapor or other condensable vapor into the mold 500. The tube or pipe 600 is held in a fixed position in the mold support base 512b by means of clamps 513 as shown in FIG. Figure 12. The tube or the pipe 500 is connected by means of a flexible or rigid conduit suitable to the steam generator such as the steam generator 110 described above in relation to figures 1-1-4. The mold support plate 512p includes a first group (three are shown) of separate rotating wheels 512f that rotatably support the outer circumference of the rotating nest 512n. The mold support plate 512p also includes a second group (three are shown) of rotating wheels 512g peripherally spaced in which it is held to rotate the closure plate 512s of the rotary nest 512n. The rotary nest 512n is thus supported laterally by means of wheels 512f and from below of the wheels 512g for rotating in relation to the lower mold support base 512. Each of the wheels 512f is supported by bearings (not shown) on a vertical pin S1 mounted on the plate 512p. Each wheel 512g is supported by the bearings (not shown) on a side pin S2 shown on the support plate 512p. The rotary nest 512n includes a generally cylindrical recess R upwardly configured to receive the collar 500d of the mold 500 as shown in Fig. 10. The mold jaw and rotation mechanism 510 include a shaft 510 having the end 510e which is engaged by friction in the collar 500c of the mold 500. For this purpose, the end 510e can be made of rubber or other material to achieve the frictional coupling with the mold of the mold 500c in such a way that rotation can be imparted to the mold by rotation medium of the 510s axis. The shaft 510s is rotatable by causing its upper end pinion 510 f to engage a drive chain 510c. The chain is driven by means of an output pinion 513s of a conventional reduction mechanism GR1 driven by means of a conventional electric or hydraulic motor M1 which is arranged on a horizontal fixed plate p1 of the frame F. The axis 510s is supported for its rotation by means of the support blocks 510b fixed on a frame plate said vertical P2, which is fixed to a frame plate P1. In this way the mold 500 caught between the jaw of the mold and the rotation mechanism 510 and the supporting mechanism of mold 512 can be rotated by means of axis 510s. The mold jaw and rotation mechanism 510 can be moved up and down in relation to the mold support mechanisms 512 by means of a vertical sliding shaft 700s guided at a lower end in a fixed housing H1 by means of a pair of bearings 700b and an upper end in a fixed housing H2. An air cylinder (not shown) is brought into contact between frame 512 (e.g. plate P3) and mechanism 510 (e.g. shaft 700s) in a manner that elevates mechanism 510 to allow placement of a mold in the apparatus and lowering the mechanism 510 so that it fixes the mold in its place. When the air cylinder is in the raised position, an anti-rotation shaft 800s exits the anti-rotation guide tube 800t to allow the mechanism 510 to rotate laterally out of the path to facilitate loading of a new mold into the apparatus . A main shaft 550 is rotatably mounted on the frame F by means of support blocks 552 so as to be able to rotate or pivot about its longitudinal axis, which is perpendicular to the longitudinal axis of the mold 500. A support sleeve with a square cross section 553 is fixed, for example by means of welding, on the shaft 550 to rotate therewith. The frame arms A carrying the mold support mechanism 512 are fixed for example by means of welding the sleeve 552 so that they rotate or pivot with the shaft 550. The mold clamp mechanism and rotation 510 are fixed to the sleeve 553 by middle of shaft 550, anti-rotation axle 800s, and the air cylinder. The mold and rotation clamp mechanism 510 and the mold support mechanism 512 are thus mounted on the sleeve 553 so that they rotate or pivot with the shaft 550. The shaft 550 is rotated or pivoted by means of a conventional electric drive motor M2 connected to the end of the shaft 550 by means of a reducing mechanism GR2. The reductive mechanism GR2 is connected to the frame of the machine 512 by means of a reaction link L 'which prevents the redoubt mechanism from rotating with the shaft. The drive motor can be of the stepped motor type. The drive motor M2 can thus rotate or pivot the shaft 550 in a staggered or continuous manner about its longitudinal axis. In this way the mold 500 caught between the jaw of the mold and the rotation mechanism 510 and the support mechanism of the mole 512 can be tilted in relation to the gravity as shown in Figure 10 while the mold is rotated.

During operation the apparatus the mold 500 having the fugitive pattern and the nozzle is placed in the rotary nest 512n with its lower collar 500d received in the recess R of the rotary nest 512n. Then, the end 510e of the shaft 510s of the mold clamp and the rotation mechanism 510 is reduced to engage with the end 510e in the upper collar 500c of the mold 500 so that rotation of the shaft 510s imparts rotation to the mold. The flow of water vapor to the pipe and tube 600 starts. The steam flow is introduced into the mold by means of a pipe or pipe 600. The steam may include the surfactant FS described before in connection with Figures 1-4, or the surfactant may be omitted in certain situations of withdrawal from the model. The main shaft 550 is pivoted to tilt the mold jaw and the rotation mechanism 510 and the mold support mechanism 512, and thus the mold 500, at any desired angle of inclination relative to gravity, see figure 10. The The angle of inclination of the mold and the rotational speed of the mold can be adjusted as required to drain the molten wax from the mold cavities MC. In this form, the wax can be drained uniformly from all the mold cavities MC positioned around a central nozzle P. This aspect of the invention thus allows the wax to be braked out of the mold cavities even though a substantial volume of a The mold cavity is below the level of gate G when the mold is in the vertical position. The molten wax is drained away from the bottom of the mold and captured in a tray (not shown). The mold 500 can be rotated while the mold is kept inclined at a fixed angle of inclination in relation to gravity. Alternatively, the mold can be inclined increasingly at selected inclination angles while the mold is rotated at each inclination angle or continuously. In addition, the mold can be continuously tilted while being rotated continuously or intermittently. The implementation of the method depends on the shape of the models that are melting (removing). It may be typical to start with the removal of the wax of the non-rotating vertical mold and then move to the wax removal of the tilted rotating mold as the removal proceeds to portions of the mold hanging below the gate orifice. The angle of inclination of the mold, the speed of rotation and the duration in time depends on the shape of the models that are melting. Water vapor or other condensable vapor is introduced via the tube or pipe 600 into the mold 500 to heat and melt the fugitive model and the nozzle while the mold is subjected to a combination of rotation and inclination, although this aspect of the invention or is limited to the use of water vapor or other condensable vapor to heat and melt the model and the nozzle. For example hot air or a stream of gas can be introduced into the mold in a manner that heats and fuses the model while the mold is subjected to a combination of rotation and inclination. The mold can also be located in an oven for instant heating of the model while the mold is subjected to a combination of rotation and tilting. Furthermore, a chemical dissolving medium can be introduced into the mold to contact and dissolve the model while the mold is subject to a combination of rotation and inclination. The invention is advantageous for removing one or more fugitive models from a refractory mold for metal casting, which may have any thickness of mold wall and which may or may not be supported by means of a particular outdoor medium that surrounds The invention is also advantageous for removing one or more fugitive models while avoiding saturation of the mold wall with condensed water vapor. The invention can be implemented to reduce fractures in the mold during the removal of the model and to allow the use of thin-walled molds without the mold fracturing. Those skilled in the art will appreciate that the invention is not limited to the embodiments described above that changes and modifications may be made within the spirit of the invention as described in the appended claims.

Claims (37)

1. CLAIMS 1. A method to remove a fugitive model inside a refractory mold that consists of introducing a condensable vapor, and a surfactant inside the mold to make contact and melt the material of the model, to condense the condensable vapor inside the mold where it makes contact and melts the model, and drains the condensed steam and molten model material out of the mold, the surfactant improves that drainage.
2. 2. A method for removing a fugitive model within a refractory mold consisting of introducing a condensable vapor and a surfactant into the mold to contact and melt the model, such as water vapor, which in a particular embodiment includes a surfactant within of the mold to make contact and melt the material of the model, while the outside of the mold is subjected to an atmosphere of non-condensing gas, condensing the condensable vapor inside the mold where it makes contact and melts the model, while the exteiror of the mold it remains free of condensed steam and drains the condensed steam and molten model material out of the mold, the surfactant improves that drainage.
3. 3. The method of claim 2 wherein the type and amount of surfactant is selected to reduce the surface tension between the condensed vapor and the pattern material.
4. 4. The method of claim 2 wherein the condensable vapor is water vapor.
5. 5. The method of claim 2 wherein the material of the model is wax, with and without a filling that is not wax.
6. The method of claim 2 wherein the surfactant is added to the condensable vapor before the condensable vapor leaves a discharge tube and enters the mold.
7. The method of claim 2 wherein the surfactant is added to the condensable vapor after the condensable vapor leaves a discharge tube and enters the mold.
8. The method of claim 7 wherein the surfactant can be transported in a dilute form using any liquid vehicle that is compatible with a non-aqueous condensable vapor that is being used.
9. The method of claim 2 in which a pressure differential between the condensable vapor within the mold and the non-condensing gas atmosphere outside the mold is small enough to prevent the condensable gas from flowing out of the mold and the non-condensing gas enters the mold cavity.
10. The method of claim 2, wherein the condensable vapor and the non-condensing gas atmosphere are substantially at the same pressure.
11. The method of claim 2 wherein the condensable vapor is water vapor.
12. 12. The method of claim 2 wherein the non-condensable gas is air.
13. 13. The method of claim 2 wherein the vapor Condensable is supplied from a source to a discharge tube from which it is discharged into the mold.
14. The method of claim 2, wherein the condensable vapor is discharged into the mold at atmospheric pressure.
15. The method of claim 2 wherein the condensable vapor is discharged into the mold under superatmospheric or subatmospheric pressure and a non-condensing gas at substantially the same superatmospheric or subatmospheric pressure is provided outside the mold in a container containing the mold .
16. 16. The method of claim 15 which includes preventing condensable vapor from entering from the outside of the container to the mold by using a seal between the mold and the container.
17. 17. The method of claim 2, wherein the fugitive model consists of wax.
18. The method of claim 2 wherein the axis of the mold containing the fugitive model is tilted with respect to the direction of gravity during casting of the fugitive model or after the fugitive model has been cast and the mold is rotates around a second axis.
19. The method of claim 2, which initially includes discharging the condensable vapor into a hollow nozzle of the model.
20. 20. The method of claim 19 wherein the hollow nozzle is made in a fugitive model prior to discharge of the condensable vapor.
21. The method of claim 20 wherein the hollow nozzle is formed by means of the condensable vapor discharged against an exposed end of the solid nozzle.
22. 22. The method of claim 2 wherein the exterior of the mold is surrounded by a medium of support particles in a container.
23. 23. The method of claim 2 wherein the exterior of the mold is not surrounded by a medium of support particles.
24. 24. An apparatus for removing a fugitive model from within a refractory mold, comprising means for introducing a condensable vapor at atmospheric, superatmospheric or subatmospheric pressure into the mold to contact and melt the pattern material and means to provide a surfactant in the condensable vapor.
25. 25. The apparatus of claim 24 wherein the means for introducing a condensable vapor comprises a discharge tube communicated to the interior of the mold.
26. 26. The apparatus of claim 24 including a surfactant feed line for supplying the surfactant to the discharge tube.
27. 27. The apparatus of claim 24 which includes a surfactant discharge tube for introducing the surfactant to the condensable vapor after it is discharged from the discharge tube.
28. 28. A method for removing a fugitive model from within a refractory mold, comprising melting or dissolving the fugitive model and subjecting the mold to a combination of rotation and tilting to improve drainage of the model material from the mold.
29. 29. The method of claim 28 wherein the mold is rotated about its longitudinal axis while the longitudinal axis is inclined with respect to gravity.
30. 30. The method of claim 28 wherein the refractory mold comprises a shell mold.
31. 31. The method of claim 30 wherein the shell mold is not surrounded by particles.
32. 32. The method of claim 30 wherein the shell mold is surrounded by particles.
33. 33. The method of claim 28 wherein the fugitive model is melted by introducing water vapor or condensable vapor into the mold.
34. 34. An apparatus for removing a fugitive model from within a refractory mold, comprising a clamp for the mold and the rotation mechanism and a mold support mechanism between which the mold is disposed, a pivotable axis in which they are arranged the jaw of the mold and the mechanism of rotation and the mechanism of support of the mold in relation to the gravity, and means to remove the fugitive model.
35. 35. The apparatus of claim 34 wherein the jaw of the The mold and the rotation mechanism comprise a rotary shaft having an end engaged by friction at one end of the mold to impart rotation.
36. 36. The apparatus of claim 35 wherein the mold jaw and the rotation mechanism move up and down relative to the mold to engage with the mold end.
37. 37. The apparatus of claim 35 in which the mold supporting mechanism comprises a rotating nest that receives an opposite end of the mold.